(Note to my players: you can read this. It won’t have any spoilers.)
Preparing Keep on the Shadowfell for running three players through seems fairly straightforward. Cracking open the Dungeon Master’s Guide, it looks like the basic idea of encounter design is to pick an xp total for an encounter and then spend that xp budget on monsters and traps.
So, in reducing the difficulty of encounters meant for five players so that they can be enjoyed by three players, I just have to reduce the xp budget. This can be accomplished by a combination of (1) reducing the number of foes faced and (2) reducing the levels of the foes faced. The first is really easy. Cutting a monster here and there is trivial. The second isn’t too bad, either. According to the DMG, reducing a monster’s level by one is simply a matter of knocking off a few hit points and reducing its attacks and defenses by one each. If this works, it is remarkably easy. Reducing the level of elite or solo enemies is only a little trickier.
I’m hoping that this actually does result in well-balanced encounters.
Also, my editing tool of choice here is the Post-It note. I don’t want to write in the module itself – in part due to habit and in part due to the fact that the paper is glossy magazine-paper that is a pain to write on. Instead, I’ve just been jotting things I want to change onto Post-Its.